JP2774351B2 - Organic thin-film electroluminescence device and method of manufacturing the same - Google Patents

Description

The present invention relates to an organic thin-film electroluminescence device and a method for manufacturing the same, and more particularly, to an organic thin-film electroluminescence device having heat resistance and long life and patterning by photoetching. The present invention relates to a method for manufacturing an organic thin-film electroluminescence device that can be used.

[Problems to be solved by conventional technology and invention]

Electroluminescent elements (hereinafter, sometimes referred to as EL elements) are characterized by high visibility due to self-emission and excellent impact resistance because they are completely solid elements. Various EL devices using a compound for a light emitting layer have been proposed and put to practical use. Among these, various materials are being developed for the organic thin film EL element because the applied voltage can be greatly reduced.

For example, an organic EL device comprising an anode / triphenylamine derivative / light-emitting layer / cathode described in JP-A-59-194393 is excellent in low voltage application, multicolor display, high brightness, high efficiency and high efficiency. It is. However, for example, a device using an aluminum complex of 8-hydroxyquinoline in the light-emitting layer is 50 devices.
When driven at a luminance of cd / m ² , the lifetime is about several hundred hours, which is a barrier to practical use.

One of the causes is thermal degradation. The 8-hydroxyquinoline-aluminum complex is a compound having relatively high heat resistance, but thermal degradation could not be avoided.

In recent years, various devices using a low-molecular organic vapor-deposited film for a light-emitting layer have been manufactured. For example, an EL device composed of an anode, a styrylamine light-emitting layer, an electron injection layer, and a cathode is known as Appl. Phys. Lett 55 (1989) 1489. However, the low-molecular organic compounds used for these low-molecular-weight evaporated films are 30
Many have a low melting point of 0 ° C. or less, and the amorphous film has a glass transition temperature of up to 100 ° C. Since all have a problem in heat resistance, thermal deterioration cannot be avoided.

Although the behavior of the thermal degradation has not been studied in detail, it is considered that the cause is crystallization, melting, enlargement of pinholes, peeling of the layer, etc. of the light emitting layer caused by heat generated by Joule heat of the device.

Furthermore, the light-emitting layer made of organic low molecules is often soluble in a solvent, and even if it is insoluble, it cannot be subjected to photoetching because it is deteriorated by peeling off with the solvent. Therefore, patterning is difficult, which is an obstacle when a display or the like is converted into an EL element.

In addition, there is a report (Polymer, 24 (1983) 755) that an element obtained by thinning polyvinyl carbazole by a spin coating method exhibited electroluminescence. The light emission luminance and film thickness of this device are 1 cd / m ² or less and several μm, respectively.
m.

[Means for solving the problem]

Therefore, the present inventors have solved the above disadvantages of the prior art,
The development of an EL device that has a simple structure, excellent heat resistance, and can obtain highly efficient light emission, and is easy to pattern
We worked diligently to develop a manufacturing method for EL devices.

As a result, a monomer having a function of an electroluminescent light emitting layer is vapor-deposited, and then polymerized by a vapor deposition polymerization method developed from a vapor deposition method of polymerizing the monomer, and the luminous efficiency is increased by using this polymer as a light-emitting layer. It has been found that an EL element having excellent heat resistance can be obtained without impairment, and that patterning by photoetching can be performed by performing polymerization in a specific process. The present invention has been completed based on such findings.

Here, the light emitting layer in the EL device of the present invention has the following three functions. These three are collectively called a light emitting layer function. Injection function When an electric field is applied, holes can be injected from the anode or the hole injection / transport layer, and electrons can be injected from the cathode or the electron injection / transport layer. Transport function Injected charges (electrons and holes) ) The function of moving the) by the force of an electric field. Light-emitting function Provides a field for recombination of electrons and holes, and connects it to light emission. However, there is a difference between the ease of hole injection and the ease of electron injection. Although the transport ability represented by the mobility of holes and electrons may be large or small, it is preferable to transfer either one of the charges.

Further, a monomer having at least one of a charge injection function and a charge transport function is polymerized by a vapor deposition polymerization method,
It has also been found that by using a polymer as a charge injection layer or a charge transport layer, an EL element having excellent heat resistance can be obtained.

That is, the present invention provides a light emitting layer material or a charge injection layer material (charge transport layer material) having a thickness of 0.5 μm formed by a vapor deposition method having at least one of a light emitting layer function, a charge transport function and a charge injection function of electroluminescence.
A thin film electroluminescent element comprising a heat-resistant polymer thin film having a glass transition temperature of 200 ° C. or higher, a step of forming an electrode on a substrate, a step of forming a charge transport layer, A charge injection function, a charge transport function, or a light emitting layer function required for electroluminescence during a structural step of an organic thin film electroluminescent element having a step of forming a light emitting layer and a step of forming a counter electrode as single or multiple steps. As a step of preparing a light-emitting layer or a charge transport layer having at least one of the following, a heat-resistant polymer-forming monomer source having a glass transition temperature of 200 ° C. or higher is vapor-deposited, and then the monomer is polymerized to form the light-emitting layer or the charge transport layer. A method for producing a thin film electroluminescent element, comprising a step of forming a layer. .

First, the polymer thin film serving as the light emitting layer or the charge transport layer of the organic thin film EL device of the present invention can be any of various types, for example, as a heat-resistant polymer-forming monomer source, a general formula, [In the formula, X represents an organic group containing an aromatic compound. And an acid dianhydride represented by the general formula: H ₂ N—Y—NH ₂ ... [II] [wherein, Y is an EL ability (at least one of a charge injection function, a charge transport function, and a light emitting layer function) An organic group having the formula: A general formula synthesized through a polyamic acid (polyimide precursor) by reacting a diamino compound represented by [Wherein, X and Y are the same as above, and n is an integer indicating the degree of polymerization. ] Is preferably used.

Here, X in the acid dianhydride represented by the above general formula [I]
Is as described above. In particular And the like, and various acid anhydrides developed as polyimide raw materials can be used.

On the other hand, when a polymer thin film is used as the light-emitting layer, Y in the compound represented by the general formula [II] is an EL as described above.
And various organic groups having the function of the light-emitting layer, in particular, organic low-molecular-weight compound residues. Various organic low-molecular-weight compound residues can be mentioned, for example, polycyclic aromatic compound residues such as anthracene, perylene and pyrene;
No. 194393, a fluorescent whitening agent disclosed in
No. 295695, metal chelated oxanoid compounds described in Japanese Patent Application No. 63-313932, JP-A-1-2547.
No. 94, Japanese Patent Application No. 1-029681, Japanese Patent Application No. 1-068388
Stilbene compounds described in the specification, Japanese Patent Application No. 1-0068387, coumarin compounds described in the specification of Japanese Patent Application No. 1-9999, and distyryl described in Japanese Patent Application No. 1-075936. Pyrazine compounds, Jph. J. Appl. Phys. 27 (19
88) Residues of known organic low molecular weight compounds having an EL light emitting layer function, such as a naphthalimide-based fluorescent compound disclosed in L713 and the like. When the polymer thin film is used as a charge transporting layer (which is not distinguished from a charge injecting layer or a charge injecting and transporting layer), Y in the compound of general formula (II)
Is a residue composed of an organic low-molecular compound having a hole injection / transport function or an electron injection / transport function. For example, as will be described in more detail later, it is a residue composed of a phthalocyanine, porphyrin or triphenylamine derivative having a hole injecting / transporting function, or a residue composed of an oxadiazole derivative having an electron injecting / transporting function.

In the present invention, as described above, the general formula [I] and the general formula [I
It is preferable to use a highly heat-resistant polyimide having an organic EL function of the general formula [III] obtained by polymerizing the compound of the formula [I] by vapor deposition polymerization as the light emitting layer or the charge transport layer.

The synthesis of polyimide by the above vapor deposition polymerization method can be performed by various known methods, for example, vacuum 28 (1985) 43
7, J.Vac.Sci.Tecnol., A4 (1986) 369, J.Vac.Sci.Tecno
l., A5 (1987) 2253, etc.

Specifically, an acid dianhydride monomer represented by the general formula (I) and a diamino monomer represented by the general formula (II) are
A binary vapor deposition is performed in a vacuum chamber by heating each vapor deposition source to obtain a polyamic acid on a substrate, which is further heated in an inert gas and dehydrated to form a ring of the general formula [II
The polyimide represented by I] can be obtained.

The conditions for the vapor deposition are, for example, a boat heating temperature of 50 to 400.
⁵ ° C., vacuum degree 10 ⁻⁵ to 10 ⁻³ Pa, deposition rate 0.1 to 500 ° / sec, preferably 1 to 10 ° / sec, substrate temperature −50 to + 300 ° C., preferably 0 to 50 ° C., and a film thickness of 5 nm. The thickness may be selected so as to be 0.5 μm. The heating of the deposition source can be performed by appropriate means such as direct heating such as energizing a deposition boat or indirect heating by a halogen lamp tube or the like. The deposition temperature varies depending on the type of the monomer used, but is preferably set so that the acid dianhydride monomer and the diamino monomer are evaporated at a ratio of 1: 1. At this time, if any one of the monomers is excessively vapor-deposited, the monomer remains in polyimide obtained, which is not preferable. Therefore, it is preferable to feedback control the heating of the evaporation source so that the temperature becomes the set temperature. The above-mentioned conditions differ depending on the type of the compound and the target crystal structure, association structure, etc. of the molecular deposition film, and cannot be uniquely determined. preferable.

The dehydration ring closure treatment is preferably performed at a heating temperature of 100 to 400 ° C., particularly about 200 ° C., for 20 minutes or more. If the treatment time is too short or the heating temperature is too low, the polymerization may not proceed completely and the polyamic acid may remain. If it is too high, for example, the generated polyimide may be decomposed at around 500 ° C. In the case of performing patterning by photoetching described later, it is preferable to polymerize at about 100 ° C. for 10 minutes or more. As the inert gas used in the atmosphere during the dehydration ring closing treatment, it is preferable to use a dry gas containing no water, for example, nitrogen, argon, helium, or the like.

It is important and preferable that the thickness of the light emitting layer or the charge transport layer thin film obtained by polymerization is 0.5 μm or less (0.1 μm or less is possible). When the film thickness is 0.5 μm or more, the light emission luminance is remarkably reduced, and the light emission luminance becomes 10 cd / m ² or less, and in many cases, it cannot be visually confirmed in a bright place.

The light emitting layer or the charge transporting layer produced by the vapor deposition polymerization method in this manner is extremely excellent in thin film properties, has no pinholes, and satisfies the above-mentioned three functions of injection, transporting and light emission in the case of a light emitting layer. In the case of the charge transport layer, the charge transport layer satisfies the required charge injection / transport function.

In addition, examples of the heat-resistant resin light-emitting layer that can be vapor-deposited and polymerized other than the polyimide include polyamide, polyamideimide, polyurea, and polyazomethine. (Preprints of the 54th Annual Meeting of the Chemical Society of Japan, II, 1547 (1987),
Polymer, Preprints, Japan, Vol. 136, 1475 (1987), Vo
l. 36, 3021 (1987)).

For example, in the case of polyamide, the general formula And the like. Where Z is And so on. In the case of polyurea, a compound monomer of the general formula O ＝ C ＝ NZ−N ＝ C ＝ O or the like may be used (Z is the same as described above). Thermal degradation, for example, peeling of the light emitting layer due to Joule heat of the element, melting, enlargement of the pinhole, crystallization of the element occurs and the film thickness of the light emitting layer is considered to be nonuniform, but in the present invention,
Decomposition temperature is 300 ° C. or higher, preferably 500 ° C. or higher, glass transition temperature is 200 ° C. or higher, preferably 300 ° C. to 400 ° C. High heat-resistant polymer, for example, by using a polyimide obtained by vapor deposition polymerization, Deterioration behavior can be suppressed, and thermal deterioration of the organic EL element can be prevented.

 Next, a method of manufacturing an organic thin film EL device will be described step by step.

First, a substrate having transparency is preferable, and glass, transparent plastic, quartz, or the like is generally applied.
The substrate is ultrasonically cleaned using isopropyl alcohol, and preferably cleaned with UV ozone.

Next, predetermined electrodes are formed on the substrate by a vapor deposition method or a sputtering method. This electrode (anode, cathode)
It is preferable to use a metal such as gold, aluminum, and indium, an alloy, a mixture, or a transparent material such as indium tin oxide (a mixed oxide of indium tin oxide; ITO), SnO ₂ , and ZnO. A metal with a high work function or an electrically conductive compound is suitable for the anode, and a metal or an electrically conductive compound with a small work function is suitable for the cathode. Preferably, at least one of these electrodes is transparent or translucent. The electrode thickness is generally
A thickness of 10 nm to 1 μm, particularly 200 nm or less, is preferable for increasing the transmittance of light emission.

Next, a predetermined light emitting layer thin film is prepared by the above-described vapor deposition polymerization method, and a counter electrode is formed on the light emitting layer in the same manner as the above electrode, whereby an EL element having a basic configuration can be obtained.

In the present invention, a desired pattern can be formed on the light-emitting layer by performing a patterning process in an intermediate step without completely performing the polymerization process.

For example, in the case of the polyimide light emitting layer, the patterning process can be performed by the following steps.

(1) Prebaking: heat is applied in dry nitrogen gas to cause some unreacted monomers and the like to react to form a polyamic acid, which is appropriately cured. The temperature at this time should be 100 to 150 ° C. If it is higher than that, it becomes polyimide and etching becomes difficult.

(2) Positive resist coating: A positive photoresist is coated on the polyamic acid film using a spinner or the like. The thickness of the positive resist is preferably 0.5 to 2 μm.

(3) Resist pre-bake: The photoresist film is heated in dry nitrogen gas at about 100 ° C. for about 30 minutes.

(4) Exposure: UV exposure is performed using a photomask having a predetermined pattern. Exposure conditions can be selected by selecting an exposure intensity and time suitable for the photoresist film.

(5) Development / matching: The exposed portion is removed with a developer, and the polyamic acid is further etched. It is preferable to use a mixture of hydrazine-based etchant and water as the developer. At this time, if an etching solution is appropriately selected, it is possible to etch even a mostly polyimide film.

(6) Rinse drying: The remaining developing etchant is rinsed off with water or the like, and dried by blowing an inert gas, for example, a dry nitrogen gas or an argon gas.

(7) Photoresist stripping: The photoresist is stripped with a solvent such as isobutyl acetate and rinsed with isopropyl alcohol.

(8) Cure: heating under the conditions described above, and dehydrating and ring closing the polyamic acid to form a polyimide.

In this way, during the polymerization process of vapor deposition polymerization, the polymerization is stopped,
Various patterns can be formed in the light-emitting layer by photoetching.

In addition, as a laminated structure of the EL element, the above-described configuration, that is, the electrode /
In the structure of the light emitting layer / electrode, a charge injection layer (a hole injection transport layer or an electron injection transport layer) can be added between the light emitting layer and the electrode. When is used, it is preferable to form a charge injection layer after forming a light emitting layer, and to manufacture an EL element having a structure of electrode / light emitting layer / charge injection layer / electrode. Conversely, if the light-emitting layer is formed after the formation of the charge injection layer by ordinary vapor deposition of low-molecular organic compounds, the charge injection layer may melt or crystallize during polymerization during the formation of the light-emitting layer, particularly during curing. Often, it is no longer a thin film. However, the phthalocyanine- and porphyrin-based charge injection layer having a high melting point can withstand heating, so that the element having the above structure can be manufactured. Also, tri-phenylamine compounds are disclosed in JP-A-63-220251.
The compound described in the publication has a high melting point of more than three hundred
Since it has a high glass transition temperature as high as 35 ° C., it can be formed before forming the light emitting layer. Furthermore, when the polymer thin film according to the method of the present invention is used as a charge transport layer (charge injection layer), the film properties are not disturbed when the light emitting layer is formed.

In addition to the case where the organic low-molecular layer is used for the charge injection layer, for example, the case where an inorganic semiconductor is used for the charge injection layer (JP-A-2-139893, JP-A-2-196475, JP-A-2-207488) Gazette, JP-A-1-312873, JP-A-1-312873
Japanese Patent No. 312874) eliminates the above-described restriction on the element manufacturing order. That is, the heat resistance of an inorganic semiconductor layer such as crystalline or amorphous Si, SiC, CdS, ZnO or the like as disclosed in these publications is much higher than that of an organic small molecule. Therefore, even after producing these inorganic semiconductors as the charge injection layer, even if the light emitting layer shown in the present invention is produced, the charge injection layer is melted or crystallized even during the polymerization treatment at the time of forming the light emitting layer. There are few things.

In the EL device of the present invention, by providing the hole injection / transport layer or the electron injection / transport layer, the light emitting performance is further improved. Here, the hole injecting / transporting layer (a hole injecting layer or a hole transporting layer, and the two are not distinguished) is made of a hole transporting compound (hole injecting material) and injected from the anode. It has a function of transmitting holes to the light emitting layer (that is, a hole injection function and a hole transport function). By sandwiching this layer between the anode of the EL element and the light emitting layer, more holes are injected into the light emitting layer at a low voltage, and the luminance of the element is improved.

The hole transport compound of the hole injection transport layer used here is disposed between two electrodes to which an electric field is applied, and when holes are injected from the anode, the holes are appropriately transmitted to the light emitting layer. Is a compound that can be By interposing the hole injection transport layer between the anode and the light emitting layer, many holes are injected into the light emitting layer with a lower electric field. Further, electrons injected from the cathode or the electron injection / transport layer into the light emitting layer are accumulated near the interface in the light emitting layer due to the electron barrier existing at the interface between the light emitting layer and the hole layer, and the light emission efficiency is improved. Presently preferred hole transport compound when a layer is placed between the electrodes given an electric field ^of 10 ⁴ to 10 ⁶ volts / cm, having a hole mobility of at least 10 ^-6 cm ² / volt sec. Therefore, preferred examples include various compounds used as a hole charge transporting material in a photoconductive material.

Examples of such charge transport materials include the following.

U.S. Pat.No. 3,112,197, triazole derivative, U.S. Pat. Nos. 3615402, 3820989, 3542544 and JP-B-45-555, 51-10983, and JP-A-51-93224, 55-17105, 56-4148, 55
Polyarylalkane derivatives described in JP-A-108667, JP-A-55-156953, JP-A-56-36656 and the like; U.S. Patent Nos. 3,180,729 and 4,278,746;
-88064, 55-88065, 49-105537, 55-51
Nos. 086, 56-80051, 56-88141, 57-45545
Pyrazoline derivatives and pyrazolone derivatives described in U.S. Pat. Nos. 6,115,105, 54-112637, 55-74546, and the like.
46-3712, 47-25336 and JP-A-54-534.
Phenylenediamine derivatives described in JP-A-35-54, JP-A-54-110536, JP-A-5-199925 and the like; U.S. Patent Nos. 3,567,450, 3,180,703, 3,240,597;
Nos. 3,658,520, 4,322,103, 4,117,961 and 4,012,376, and JP-B-49-35702, JP-A-39-27577, and JP-A-55-144250, JP-A-56-119132, and JP-A-56-119. 22437
JP-A No. 1110518, an arylamine derivative described in U.S. Pat.No. 3,235,501, an amino-substituted chalcone derivative described in U.S. Pat. Oxazole derivatives, styryl anthracene derivatives described in JP-A-56-46234, etc., fluorenone derivatives described in JP-A-54-110837, etc., U.S. Pat. 54-59143, 5
5-52063, 55-52064, 55-46760, 55-85
Hydrazone derivatives described in JP-A-495-57, JP-A-57-11350, JP-A-57-148749, etc., and JP-A-61-210363, JP-A-61-228451, JP-A-61-14642.
Nos. 61-72255, 62-47646, 62-36674,
No. 62-10652, No. 62-30255, No. 60-93445, No. 60
Stilbene derivatives and the like described in JP-A-94462, JP-A-60-174749, JP-A-60-175052 and the like can be listed.

More particularly preferred examples include a compound (aromatic tertiary amine) as a hole transport layer and a compound (porphyrin compound) as a hole injection zone disclosed in JP-A-63-295695. .

Further preferred examples of the hole transport compound are described in JP-A-53-27033, JP-A-54-58445, and JP-A-54-149634.
JP-A-54-64299, JP-A-55-79450, and 55
No. 144250, No. 56-119132, No. 61-295558, No. 61-98353, and U.S. Pat. No. 4,127,412. Examples of these are as follows.

A hole injecting and transporting layer is formed from these hole transporting compounds, and the hole injecting and transporting layer may be composed of a single layer or a layer in which a hole injecting and transporting layer using a different kind of compound is stacked. Is also good. As described above, one of the aspects of the present invention is that a polymer thin film can be a hole injecting and transporting layer if a low molecular compound having hole injecting and transporting properties is used as the residue Y of the general formula (III). On the other hand, the electron injecting and transporting layer (electron injecting layer) is composed of a compound that has a function of transmitting electrons (the electron injecting function and the electron transporting function are not distinguished). Preferred examples of the electron transfer compound (electron injection material) for forming the electron injection transport layer include: Nitro-substituted fluorenone derivatives such as JP-A-57-149259, JP-A-58-55450 and JP-A-63-104061.
No. 3 (1988), p.68, anthraquinodimethane derivatives described in Japanese Unexamined Patent Publication No.
Listed in 1 etc. Diphenylquinone derivatives such as, Thiopyran dioxide derivatives such as those described in JJAPPl. Phys., 27, L269 (1988), etc. Compounds represented by the following formulas: JP-A-60-69657, JP-A-61-143764, JP-A-61-148159
And the anthraquinodimethane derivatives and anthrone derivatives described in JP-A-61-225151 and JP-A-61-233750. The oxadiazole derivative represented by these can be mentioned.

As described above, one of the aspects of the present invention is that if a low molecular compound having an electron injecting function is used as the residue Y, the polymer thin film can serve as an electron injecting and transporting layer.

In the EL element of the present invention, when the applied voltage is AC (AC drive), light emission is observed only in a bias state in which a positive voltage is applied to the anode side. When the applied voltage is direct current (direct current drive), light emission is always observed by applying a positive voltage to the anode side.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

Example 1 (Synthesis of monomer having EL light emitting layer function) The compound represented by the above formula is converted to a known literature Polymer Prepri
nts.Japan 37 (1988) 770 and Polymer Preprints.Japan
38 (1989) 447, recrystallized from benzene and purified. The melting point of this compound was 301-305 ° C.

(Vaporization polymerization of light emitting layer) 500 mg of the above monomer was placed in one deposition source of a vacuum deposition apparatus, and a commercially available (manufactured by Aldrich) pyromellitic dianhydride (the following formula) was placed in the other deposition source.

In addition, as a substrate, a white sheet glass (HOY
(Company A), washed with isopropyl alcohol, blown dry with dry nitrogen gas, and further washed with UV ozone.

The substrate was kept at room temperature, and the evaporation sources were simultaneously heated by a halogen lamp, and each was controlled to evaporate at 4 ° / sec. While keeping the deposition rate constant, the deposited film on the substrate was
When the mark was displayed, the deposition was stopped.

Next, the sample taken out of the vacuum chamber was heated (cured) at 200 ° C. for 40 minutes in an oven in a dry nitrogen atmosphere to complete vapor deposition polymerization.

(Confirmation of Polyimide Formation) The same operation as above was performed using a NaCl single crystal as a substrate to form a vapor-deposited polymer film having a thickness of 2 μm.

When an IR spectrum was measured using this sample, 17
80cm ^-1, 1720cm ^-1, absorption peaks due to imide bond was present in 1380 cm ^-1. This peak appears after curing, proving that polyimide has been formed by curing. Also, the peak of the acid anhydride present before curing (1790
cm ^-1, 1850 cm ^-1 vicinity ones) has been suggested a residual monomer had disappeared after curing. Further, in order to confirm the heat resistance of this film, the NaCl substrate was dissolved and removed with water, and then measured by DSC (differential thermal analyzer) and TGA (thermogravimetric analyzer). As a result, the glass transition point was 3 according to DSC.
By TGA, the decomposition temperature was 480 ° C, confirming high heat resistance.

(Preparation of EL element and confirmation of light emission) An Mg: In electrode was deposited on the light emitting layer formed on the glass substrate. The deposition rate of Mg was set at 30 ° / sec, and the deposition rate of In was set at 3-4 ° / sec.

Next, when a direct current of 9 V was applied with the ITO electrode being positive and the Mg: In electrode being negative, an EL element was produced.

Example 2 (Synthesis of hole injection layer material) A triphenylamine compound having a high glass transition point and a melting point of 323 ° C (the following formula) was synthesized according to Synthesis Example IV of JP-A-63-220251.

Next, according to the FD mass spectrum, m / e = 1322
The (M ^* ) white solid was isolated after purification on silica gel. Melting point was 323-324.5 ° C.

(Preparation of EL Device and Confirmation of Light Emission) 500 mg of the above triphenylamine compound was placed in a molybdenum vapor deposition boat, and this was energized to vapor-deposit 700 ° on the same substrate as in Example 1. Further, in the same manner as in Example 1, a polyimide light emitting layer was formed at 650 °. However, curing was performed at 150 ° C. for 10 hours so as not to break the film state of the hole injection layer made of a triphenylamine derivative, which is a thin film.
Further, an Mg: In electrode was formed in the same manner as in Example 1 to produce an element.

The element was energized in the same manner as in Example 1 to obtain a bluish green emission luminance of 20%.
It has been confirmed that 0 cd / m ² can be reached. At this time, the current density was 15 mA / cm ² , the applied voltage was 5 V, and the luminous efficiency was 0.84 lm.
/ W. The device was dried in dry argon to
A life test was performed at 100 cd / m ² . After emitting light for about 2700 hours, the initial luminance was reduced to half of that of the conventional technology, and the life was greatly exceeded.

Example 3 (Formation of hole injection transport layer) (Synthesis of triphenylamine derivative) The diaminotriphenylamine derivative of the above formula was synthesized according to a conventional method. First, 3,3'-dinitrotriphenylamine was synthesized according to the document Bull. Soc. Jpn. 59 (1986) 803. This compound can also be synthesized from aniline and p-fluoronitrobenzene by Ullman condensation. The melting point of this compound was 145-146 ° C.

Next, this compound was reduced by a known reduction method using iron hydrochloride to obtain 3,3'-diaminotriphenylamine.

(Polymerization Formation of Charge Transport Layer (Hole Injection Layer)) 500 g of the monomer (3,3'-diaminotriphenylamine) obtained in the above synthesis was placed in one of the evaporation sources of a vacuum evaporation apparatus. Further, 2 g of commercially available terephthalic acid chloride was placed in the other evaporation source.

A 1000 ° ITO white glass substrate washed in the same manner as in Example 1 was kept at room temperature, and the vacuum chamber was evacuated to a vacuum of 10 ^-6 Torr. Of the evaporation sources, terephthalic acid chloride was heated by a halogen lamp, and it was confirmed that the vacuum pressure became 10 ^-4 Torr. At this time, the deposition source containing the triphenylamine derivative (3,3'-diaminotriphenylamine) was heated until the deposition rate reached 4 ° / sec. The vapor deposition polymerization was stopped when the crystal oscillator thickness gauge on the substrate showed 700 °.

The polymer thin film formed as described above was peeled off, and an absorption peak due to an amide group was confirmed by a KBr pellet method (1650).
cm ^-1 ). This produced a polyamide thin film with triphenylamine in the structure.

Example 4 (Production of EL element) In the same manner as in Example 3, a polyamide thin film as a hole injection / transport layer was produced. Next, Al (Ox) ₃ (O
An x: oxin) complex layer was formed (film thickness: 600 °).

Further, an Mg: Cu electrode was formed by an evaporation method. ITO as positive electrode, M
g: When the Cu electrode was used as a negative electrode and a DC voltage of 8 V was applied, 50
A current of mA / cm ² flowed, and green light emission (yellow) with a luminance of 1300 cd / m ² was obtained.

As described above, Examples 3 and 4 confirmed that the charge transport layer could be formed by vapor deposition polymerization.

〔The invention's effect〕

As described above, since the organic EL device of the present invention can be formed with a light-emitting layer having higher heat resistance than a conventional EL device, it is possible to suppress thermal deterioration and extend the life. Further, according to the method of the present invention, it is possible to perform patterning of the light emitting layer, which has been conventionally difficult, and it is possible to manufacture EL elements having light emitting layers of various patterns by photoetching.

Therefore, it is possible to provide an inexpensive and stable product as an EL element for display of various devices, such as an EL element for a display.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-216998 (JP, A) JP-A-3-20992 (JP, A) JP-A-1-243393 (JP, A) JP-A-2- 267889 (JP, A) JP-A-2-78187 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 33/10 H05B 33/14 H05B 33/22

Claims (6)

(57) [Claims] 1. A light emitting layer material or a charge injection layer material having at least one of an electroluminescence light emitting layer function, a charge transport function and a charge injection function, having a thickness of 0.5 μm or less formed by a vapor deposition method, and Glass transition temperature 2
A thin-film electroluminescent device using a heat-resistant polymer thin film at a temperature of 00 ° C. or higher. 2. The thin-film electroluminescence device according to claim 1, wherein the light-emitting luminance of the polymer thin film having a light-emitting layer function is 10 cd / m ² or more. 3. The thin-film electroluminescent device according to claim 1, wherein the polymer thin film is made of polyimide. 4. An organic thin-film electroluminescence device having a step of forming an electrode on a substrate, a step of forming a charge transport layer, a step of forming a light emitting layer, and a step of forming a counter electrode as a single step or a plurality of steps. During the manufacturing process, a heat-resistant polymer having a glass transition temperature of 200 ° C. or higher is used as a light-emitting layer or a charge-transport layer having at least one of a charge injection function, a charge transport function, and a light-emitting layer function required for electroluminescence. A method for producing a thin-film electroluminescent device, comprising a step of forming a light-emitting layer or a charge transport layer by vapor-depositing a formable monomer source and then polymerizing the monomer. 5. A step of depositing a heat-resistant polymer-forming monomer source having a function of an electroluminescent light-emitting layer, and then patterning the light-emitting layer after polymerizing the monomer to form a light-emitting layer. 5. The method for manufacturing a thin-film electroluminescence device according to 4. 6. A heat-resistant polymer-forming monomer source having an electroluminescent light-emitting layer function is deposited, and the polymerized layer formed while polymerizing the monomer to an extent capable of photoetching is patterned by photoetching. 5. The method for manufacturing a thin film electroluminescent device according to claim 4, further comprising a step of completing polymerization to form a patterned light emitting layer.